Btrfs: add a plugging callback to raid56 writes

[linux-imx.git] / fs / btrfs / raid56.c

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 7ccddca9ee713dd1766d4eace8df7819b9e64578..e34e568534d930dac561a24ed4a48db282b4c221 100644 (file)
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -97,9 +97,10 @@ struct btrfs_raid_bio {
        struct bio_list bio_list;
        spinlock_t bio_list_lock;
 
-       /*
-        * also protected by the bio_list_lock, the
-        * stripe locking code uses plug_list to hand off
+       /* also protected by the bio_list_lock, the
+        * plug list is used by the plugging code
+        * to collect partial bios while plugged.  The
+        * stripe locking code also uses it to hand off
         * the stripe lock to the next pending IO
         */
        struct list_head plug_list;
@@ -1557,6 +1558,103 @@ static int __raid56_parity_write(struct btrfs_raid_bio *rbio)
        return full_stripe_write(rbio);
 }
 
+/*
+ * We use plugging call backs to collect full stripes.
+ * Any time we get a partial stripe write while plugged
+ * we collect it into a list.  When the unplug comes down,
+ * we sort the list by logical block number and merge
+ * everything we can into the same rbios
+ */
+struct btrfs_plug_cb {
+       struct blk_plug_cb cb;
+       struct btrfs_fs_info *info;
+       struct list_head rbio_list;
+       struct btrfs_work work;
+};
+
+/*
+ * rbios on the plug list are sorted for easier merging.
+ */
+static int plug_cmp(void *priv, struct list_head *a, struct list_head *b)
+{
+       struct btrfs_raid_bio *ra = container_of(a, struct btrfs_raid_bio,
+                                                plug_list);
+       struct btrfs_raid_bio *rb = container_of(b, struct btrfs_raid_bio,
+                                                plug_list);
+       u64 a_sector = ra->bio_list.head->bi_sector;
+       u64 b_sector = rb->bio_list.head->bi_sector;
+
+       if (a_sector < b_sector)
+               return -1;
+       if (a_sector > b_sector)
+               return 1;
+       return 0;
+}
+
+static void run_plug(struct btrfs_plug_cb *plug)
+{
+       struct btrfs_raid_bio *cur;
+       struct btrfs_raid_bio *last = NULL;
+
+       /*
+        * sort our plug list then try to merge
+        * everything we can in hopes of creating full
+        * stripes.
+        */
+       list_sort(NULL, &plug->rbio_list, plug_cmp);
+       while (!list_empty(&plug->rbio_list)) {
+               cur = list_entry(plug->rbio_list.next,
+                                struct btrfs_raid_bio, plug_list);
+               list_del_init(&cur->plug_list);
+
+               if (rbio_is_full(cur)) {
+                       /* we have a full stripe, send it down */
+                       full_stripe_write(cur);
+                       continue;
+               }
+               if (last) {
+                       if (rbio_can_merge(last, cur)) {
+                               merge_rbio(last, cur);
+                               __free_raid_bio(cur);
+                               continue;
+
+                       }
+                       __raid56_parity_write(last);
+               }
+               last = cur;
+       }
+       if (last) {
+               __raid56_parity_write(last);
+       }
+       kfree(plug);
+}
+
+/*
+ * if the unplug comes from schedule, we have to push the
+ * work off to a helper thread
+ */
+static void unplug_work(struct btrfs_work *work)
+{
+       struct btrfs_plug_cb *plug;
+       plug = container_of(work, struct btrfs_plug_cb, work);
+       run_plug(plug);
+}
+
+static void btrfs_raid_unplug(struct blk_plug_cb *cb, bool from_schedule)
+{
+       struct btrfs_plug_cb *plug;
+       plug = container_of(cb, struct btrfs_plug_cb, cb);
+
+       if (from_schedule) {
+               plug->work.flags = 0;
+               plug->work.func = unplug_work;
+               btrfs_queue_worker(&plug->info->rmw_workers,
+                                  &plug->work);
+               return;
+       }
+       run_plug(plug);
+}
+
 /*
  * our main entry point for writes from the rest of the FS.
  */
@@ -1565,6 +1663,8 @@ int raid56_parity_write(struct btrfs_root *root, struct bio *bio,
                        u64 stripe_len)
 {
        struct btrfs_raid_bio *rbio;
+       struct btrfs_plug_cb *plug = NULL;
+       struct blk_plug_cb *cb;
 
        rbio = alloc_rbio(root, bbio, raid_map, stripe_len);
        if (IS_ERR(rbio)) {
@@ -1574,7 +1674,27 @@ int raid56_parity_write(struct btrfs_root *root, struct bio *bio,
        }
        bio_list_add(&rbio->bio_list, bio);
        rbio->bio_list_bytes = bio->bi_size;
-       return __raid56_parity_write(rbio);
+
+       /*
+        * don't plug on full rbios, just get them out the door
+        * as quickly as we can
+        */
+       if (rbio_is_full(rbio))
+               return full_stripe_write(rbio);
+
+       cb = blk_check_plugged(btrfs_raid_unplug, root->fs_info,
+                              sizeof(*plug));
+       if (cb) {
+               plug = container_of(cb, struct btrfs_plug_cb, cb);
+               if (!plug->info) {
+                       plug->info = root->fs_info;
+                       INIT_LIST_HEAD(&plug->rbio_list);
+               }
+               list_add_tail(&rbio->plug_list, &plug->rbio_list);
+       } else {
+               return __raid56_parity_write(rbio);
+       }
+       return 0;
 }
 
 /*